Installation, commissioning and maintenance

Always use a fully designed ductwork system – for domestic ventilation this would usually be done by the system supplier, however they may charge for this. Use the ductwork and fittings specified and don’t allow shortcuts with flexible or shallow plastic ductwork.

Cleanliness needs to be maintained during construction. Any dirt in the ductwork system will be blown into the house later. Keep ductwork covered before use and cover open ends of ductwork during construction. Do not run the fans at all until after the final clean of the house to avoid drawing dust etc. into the ductwork.

Commissioning is the job of setting the system up with the correct flow rates. This can only be done once the house is clean. Traditional branched systems need to have the flow rate for each room adjusted at the terminal, though good ductwork system design will give required settings (in mm). Semi-rigid systems may come designed with specific flow regulating inserts for the duct to each room. It is still necessary to check the flow at each terminal.

Hand over the system with a description of the system, demonstration of how to operate the controls and how to change filters. Also provide information on where to get replacement filters and written and illustrated instructions on how to change the filters when the time comes 3 or 6 months later.

The primary maintenance requirement is changing filters. Some ventilation units maintain a constant air flow rate when filters get clogged, but in so doing the fans get noisier. Older or cheaper systems just supply less air. So regular filter changes are important. Write the date of install on the filter. Most control units have a filter change indicator but this is based on number of days.

It is an advantage if occupants can periodically check the system: some systems are so quiet that occupants may not notice if the fans stop running. Over a few years dust builds up on extract valves. These can be removed and cleaned, being careful not to change airflow settings or mix valves between rooms. Terminals should be removed for redecoration, but must be labelled by room if more than one is removed.

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